# [EM] IRV vs Plurality

robert bristow-johnson rbj at audioimagination.com
Sun Jan 17 00:01:45 PST 2010

```okay, Abd ul, i once got suckered into responding to a big long thing
you made in response to me.  you probably seen it, but the list
hasn't because it exceeded some size limit.  so i'm gonna snip at the
first place to respond and i'll ask that the next issue area get its
separate email thread (we might even spawn new subject lines).  i
just can't deal with size explosion to this degree.

On Jan 17, 2010, at 12:53 AM, Abd ul-Rahman Lomax wrote:

> At 01:44 AM 1/15/2010, robert bristow-johnson wrote:
>> but the problem with considering *more* than pure ranking (Range) is
>> that it requires too much information from the voter.  and the
>> problem with *less* (Approval or FPTP) is that it obtains too little
>> information from the voter.
>
> There is a common error here, which is to assume that Range
> "requires" too much information from the voter.

well, it does force the voter to consider the questions "oh, i hate
this guy 28% more than i hate the other guy, so how do i rate each
candidate in range?"  the range rating values are a superset of the
adjacent integer rankings from a ranked-order ballot like one for
Condorcet, IRV, Borda.  in the ranked-order ballot, all the voter has
to decide is who she would vote for in adjacent candidates: A>B>C.
she doesn't have to decide how much more she likes B over C than how
much A is over B.  one is a quick set of qualitative decisions.  the
other makes it a quantitative issue, and that's when a lot of us get
out our dartboard.  i don't think making threshold decision based on
the precise sum of a bunch of noisy numbers (which is what Range is
when we use our dartboards to score a candidate) does much other than
to add the means of the noisy numbers and a sum of zero-mean random
numbers which throws a little bit of dice into the mix before using
the threshold comparison and determining the winner.

so it requires thinking that we wouldn't have to do otherwise.  if we
don't feel like thinking that seriously, it becomes a big noisy
threshold on the means of stable ranks.  that's sorta like Borda and
does become the equivalent if people's evaluations of candidates
sorta "linear".

> First of all, Approval is Range, simply the most basic Range method.

it's Range with 1-bit binary values.

> So what you have is a contradiction: "Range" requires both too much
> and too little information. Surely it depends on the specific Range
> implementation.

yes it does.   of course the answer is (if i may appeal to an audio
image) that what we *normally* mean when we say "Range" is were the
sliders for each candidate are either continuous or have many
discrete values (say 10 or 100).

a two-position slider is what we call a "switch". requires one bit of
information.  that's getting qualitatively different.  either you are
at the minimum number of levels (or bits of information in the slider
position) or you're not.

perhaps a 3-position slider can be "Actively Disapprove", "no opinion
- neutral", and "Actively Approve"

perhaps a 4-position slider can be "Actively Disapprove", "no opinion
- neutral", and "Actively Approve" and "Hey, I really like this guy!"

perhaps a 5-position slider can be "This guy is crap", "Actively
Disapprove", "no opinion - neutral", and "Actively Approve" and "Hey,
I really like this guy!"

we can continue on like this with more discrete levels and all we'll
get are gradations of the above.  it's all a matter of degree.

but the 2-position slider is a 1-bit piece of information:
"No","Yes", that's the minimum a voter has to judge.  that's
qualitatively different.  here's why:  with the multi-level (3 or
more), then order has to be considered with candidates that you
approve or disapprove.

but the multi-level or continuous slider (3+) requires *more* than
just ordering information (who is preferred to whom?), it requires
*spacing* information.  like "i hate candidate D worse than i hate C
whom i dislike more than B whom i like less than A."  you have to
decide that D is twice as badder than C than C is badder than B or
some other value judgement.  what if you just don't feel like making
such a precise judgement?  then you get your dartboard.

--

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."

```

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